Importance of Understanding Weather

The past week we have seen a number of searches across the country for missing people who got caught in weather.  As fall approaches, it is a good time to review weather patterns and things to look for, as well as ways to stay out of trouble.  Over the years I have developed a rule: whatever the weather calls for, always have rain gear (even with 0% chance of rain) and always have enough to stay warm 15 degrees below the weather report and cool 15 degrees above.  Mainly because weather reports are almost always wrong…not because weathermen suck (although it is the one job in America you can be wrong at EVERY day and not get fired), but because, frankly, weather is constantly changing and can always sneak up on you. 

Also, I recommend for those spending a lot of time outdoors a good watch that has an altimeter and barometer on it.  Some watches like the Suunto Core have a “Storm Alarm” that goes off if the baro pressure changes too much over a short timeframe.  This is very helpful, though not always right.  Just remember if using these watches that they are calculated by pressure-based altitude.  So if your altitude is wrong, as it often will be, your baro will be wrong too.  Just make sure when starting your activity to match the alto on your watch to the alto on your topo map, and you should be good to go.

Ok, here are some pointers:

Identifying Hazardous Weather

–        Check the forecast before you leave

–        VHF radio

–        Observation

–        Mobile phones

Air Masses and Pressure

–        Air moves from High to Low pressure areas causing wind

–        As winds converge near a Low, it is forced to rise, causing cooling & precipitation

–        As winds diverge near a High, it is forced to sink, causing warming & fair weather

Air Masses and Fronts

–        Warm Fronts

•          Gentle slope causing gradual rising, cloudiness, and precipitation along front

•          Generally move northward

–        Cold Fronts

•          Steep slope causing narrow band of showers along or just ahead of front

•          Generally move West to East

Cirrus Clouds

–        High-level (20,000’ +)

–        Generally fair weather

–        Lots of these in the sky may indicate the weather will change in the next 24 hours.

Nimbus Clouds

–        Mid-level (7,000’ – 15,000’)

–        Steady precipitation

Stratus Clouds

–        Low-level (0’ – 10,000’)

–        Generally grey and dull weather

Cumulous Clouds

–        Mid to high-level (7,000’ – 60,000’+)

–        Generally fair weather

–        If taller than wide, risk of thunderstorm development